Such a centrifugal separator is known from U.S. Pat. No. 6,319,186. The known centrifugal separator has a centrifuge rotor which is rotatable about a rotary axis. The rotor includes a rotor wall enclosing an inner separating space. A stationary pipe member extends through the rotor wall into the separating space. The pipe member includes an inlet channel for feeding of the product to the inner space, a first outlet channel for discharging the relatively heavy phase from the inner space, and a second outlet channel for discharging the relatively light phase from the separating space. A first chamber is provided in the rotor for collecting the relatively heavy phase. A heavy phase channel extends from a radially outer area of the separating space to the first chamber for feeding the relatively heavy phase from the radially outer area to the first chamber. A nozzle member is provided between the heavy phase channel and the first chamber for creating a controlled feeding of the relatively heavy phase from the heavy phase channel to the first chamber. A paring pipe extends outwardly in the first chamber to an outer orifice and is connected to the first outlet channel for discharging the relatively heavy phase from the first chamber out of the centrifuge rotor via the outer orifice of the paring pipe. The paring pipe is provided in a lower part of the centrifuge rotor.
SE-B-427 248 discloses different kinds of centrifugal separators for separating a product to a relatively heavy phase and a relatively light phase. The separators disclosed have a centrifuge rotor with a permanently open outlet for the separated relatively heavy phase. In order to provide an automatic control of the flow of the relatively heavy phase, a nozzle member in the form of a vortex nozzle is provided at the outlet opening. The vortex nozzle is a type of vortex fluidistor, which does not separate the incoming product but controls the flow by increasing the latter when the viscosity of the liquid increases and decreases the flow when the viscosity of the liquid decreases. Such an automatic flow control creates a throttling of the flow without leading to a too small flow area which could involve a risk for clogging of the nozzle.
In certain centrifugal separators, the relatively heavy phase, which for instance may be a sludge-like product such as yeast and which is collected in the radially outermost part of the inner separating space, is discharged out of the centrifuge rotor via one or several heavy phase channels and via a vortex nozzle of the type mentioned above. The vortex nozzle has the property of decreasing the flow resistance there through, the higher the viscosity of the relatively heavy phase is (the higher the sludge-concentration of the sludge is). The rotation of the relatively heavy phase in the vortex nozzle and thus the flow-resistance of the vortex nozzle decreases with increasing viscosity of the heavy phase. This means that the discharge of the relatively heavy phase through a heavy phase channel having such a vortex nozzle to a certain extent is self-controlling.
During internal cleaning of rotors with discharge channels of this kind and without de-mounting of the rotor, so called Cleaning In the vortex nozzles limit however the flow of the cleaning liquid having a low viscosity through the heavy phase channels and adjacent spaces.